The purpose of this study is to 1) see whether chemotherapy with PSC833 and doxorubicin (ADR) is effective in treating patients with breast cancer; 2) evaluate side effects; 3) study how p-glycoprotein interacts with PSC833 and ADR; and 4) determine how the body process both drugs. Protocol activity has been slower than anticipated. There is no preliminary data to report at this time.